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Sunday, August 16, 2015

Hibiscus Blooming but Leaves Too Small

Q. My hibiscus plant, which I planted from a pot to my
outdoor flower bed, is blooming like it should.The problem is, that the leaves are not getting any bigger than 1 -
1½" long and ¾" wide.The new
leaves also only get to that size.I
water and fertilize if with Miracle Grow regularly, but that does not
help.Any suggestions?

A. The appearance of plants will be different when
growing in different climate zones. Appearance can also be impacted by your
management practices. Let's cover a few of these.

Red hibiscus growing on our farm, Moca Family Farm, in the Philippines

Climate and Microclimates. Plants growing under high light intensities will have a
different appearance then plants growing under lower light intensities. The
principal differences are in leaf size, color and thickness.

Leaves growing
under higher light intensities, provided they are getting enough water and
nutrients, will be dark green, they will be smaller, thicker or tougher and
develop a thicker waxy coating on the leaf surface. The same plant growing
under lower light intensities will have larger and thinner leaves with a waxy
coating that is not as thick.

If light intensities get extremely high then we
will see leaf discoloration, yellowing or bronzing, on some plants because the
light intensity is actually damaging the leaves. If the same plant does not
receive enough light then the plant will become “leggy” with large distances
between the leaves and thin stems that will not support its own weight. The
plant will become "floppy".

Our job
as a manager of this plant is to find the right location in our landscape, the
right microclimate, that will give it enough light so that it will flower and
have an appearance close to what we expect. Because we are in a desert,
Hibiscus might not look exactly the same as it does in semi tropical or
tropical climates but we can approach that look if we are careful where we
plant it.

Fertilizer.
The selection of the right type of fertilizer and amount of fertilizer will, to
a large degree, influence the type of growth we get from a plant. We know for
instance that phosphorus fertilizers are very important for flowering,
fruiting, root development and production of oils in plants.

If not enough
phosphorus is present for the plant to use it will impact this type of growth.
If too much is present, it can also impact growth of plants by "messing
up" the soil chemistry. If fertilizers are applied to the soil, we
generally do not need to apply phosphorus frequently.

Nitrogen
is a different animal. Nitrogen is important for developing dark green color in
leaves and stems and for "pushing" new growth. It is important in
producing good leaf size and in the number of leaves and supporting stems
produced.

The nitrogen in soils available to plants are in "salt"
form. Applying too much nitrogen can result in leaf burning or scorching along
the edges and even plant dieback or death if excessive amounts are applied.
Unlike phosphorus, nitrogen is removed from the soil fairly quickly unless it
is in organic form.

The nitrogen will be depleted in 4 to 6 weeks through plant
uptake and removal from the soil by the irrigation water and
"evaporating" into the air. Organic nitrogen is removed much more
slowly and gives the plants a "steady feeding" of nitrogen over a
longer period of time.

In your
case you want to make sure that nitrogen is applied regularly through the
growing season to maintain dark green color and "push" new growth.
Combined with moderate amounts of shade, nitrogen will encourage more leaves
and larger leaves.

Soil. Organic
matter such as compost mixed into the soil at the time of planting and applied
at least annually to the surface of the soil surrounding the plant will
encourage more leaf production and larger leaves on those plants which have it
in their genetics to produce this kind of growth. I have seen this numerous
times on a number of plants particularly in parts of the plants that are shaded
such as lower leaves.

What do you need
to do? Understand that if your hibiscus is in a very hot, bright location
that this location will limit the plants ability to produce larger leaves.
Moderate amounts of shade will encourage larger leaf development, particularly
in a microclimate that gets morning sun but afternoon shade.

Get some compost
and dig it into the soil surrounding the plant as much as you can. Apply about
1 inch of compost to the soil surface after you are finished and thoroughly wet
the soil deeply immediately after you apply. At least once a year apply compost
to the soil surface surrounding the plant and water it in thoroughly.

Apply
phosphorus either to the soil or to the foliage as a foliar spray at least once
a year after it is finished flowering for the season. Apply high nitrogen
fertilizers to the soil surrounding the plant in early spring, early summer and
late summer. Winter tender plants should not be fertilized with high nitrogen
fertilizers after August 1.

The three overall factors that will determine the leaf
size:

what it's capable of producing genetically (if you know this plant can
produce much larger leaves but it is not doing it),

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Home. My home base is Las Vegas, Nevada, in the Eastern Mojave Desert. This blog focuses on horticulture in Deserts.

Me. Desert Horticulture is very different from horticulture in wet climates. Very few people talk about it. This blog focuses on it. My experience in horticulture span over 50 years; time as an applied academic and now working as a consultant. This blog shares my experience and advice in Desert Horticulture. Work in Northern, East and Southern Africa, Western and Central Asia and the Middle East have expanded my views on Desert Horticulture.

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